Population dynamics of whitefly (Bemisia tabaci Genn.) infesting BT cotton and their insecticidal management under field conditions

Studies were taken up to monitor the seasonal occurrence of whitefly population in cotton as well as its insecticidal management under field conditions of Institutional Research Farm, Institute of Agriculture, Visva-Bharati, Sriniketan, during the kharif season of 2018-19. Population reduction of whitefly was done with eight insecticides having different molecular composition and one untreated check. The experiment was drawn in a Randomised Block Design with three replications. The occurrence of whitefly was noticed during the fourth week of July (0.2 whitefly per plant) which continued till late December. Highest whitefly population was found during fourth week of September (12.24 Whitefly per plant). Correlation studies of whitefly population and abiotic factors suggested that whitefly population was significantly correlated with maximum temperature at 1% level of significance. Among the different insecticides tested for population reduction of whitefly in Bt cotton it was noticed that combination product of Imidacloprid 6% + Lambda Cyhalothrin 4%SL @ 500 ml/ha and 450 ml/ha proved most effective and gave 94.15% and 93.81% pest population reduction after second spray imposition respectively.